Metric left-hand bolts are designed for applications where reverse threading is needed to prevent loosening during operation. This guide highlights five durable options with left-hand threads, suitable for machinery, automotive, and construction projects. Each selection features 8.8-grade carbon steel or stainless steel, black oxide finishes, and flange or hex-head designs to maximize grip and stability. Read on to compare dimensions, thread pitch, and overall reliability for demanding environments.
| Product | Brand | Dimensions (mm) | Pitch | Material & Finish |
|---|---|---|---|---|
| uxcell M6x17mm Hex Flange Bolts Left Hand | uxcell | M6 x 17 | 1.0 | 8.8 carbon steel, black oxide |
| uxcell M10x25mm Hex Flange Bolts Left Hand | uxcell | M10 x 25 | 1.5 | 8.8 carbon steel, black oxide |
| uxcell M8x16mm Hex Flange Bolts Left Hand | uxcell | M8 x 16 | 1.25 | 8.8 carbon steel, black oxide |
| uxcell 3Pcs M8-1.25 x 20mm Left HandHex Bolts | uxcell | M8 x 20 | 1.25 | carbon steel, black oxide |
| Kozelo M8-1.25 x 50mm Left Hand Bolts | Kozelo | M8 x 50 | 1.25 | carbon steel, black oxide |
uxcell M6x17mm Left-Hand Hex Flange Bolts
These hex flange bolts use a left-hand reverse thread design to resist loosening under rotation. The M6 x 17mm size features a 13mm flange diameter and a 9.8mm hex width, with a 5mm head height for a low-profile profile. Made from forged 8.8-grade carbon steel with a black oxide finish, they offer a high load rate, hardness, and wear resistance suitable for demanding equipment assemblies. The flange acts like a flat washer, aiding firm locking during tightening.
Ideal for small assemblies where space is limited and secure retention is essential. The left-hand thread helps prevent vibration-induced loosening in specific machinery and automotive applications.
uxcell M10x25mm Left-Hand Hex Flange Bolts
Dimensioned at M10 x 25mm with a 21mm flange diameter, these left-hand bolts feature a 14mm hex width and an 8.8-grade carbon steel body finished in black oxide. The 1.5mm pitch (0.06″) provides robust engagement, while the flange design improves clamping stability by distributing load like a washer. They’re engineered for high load capacity and wear resistance, supporting long-term performance in machinery or automotive assemblies.
Suitable for applications requiring reverse-threading to maintain tightness under operation, these bolts balance strength with a compact profile for tighter fits.
uxcell M8x16mm Left-Hand Flange Bolts
This M8 x 16mm left-hand bolt set combines a compact 13mm flange diameter with a 9.8mm hex head width and 5mm head height, optimized for tight spaces. Forged from 8.8-grade carbon steel and finished in black oxide, the bolts deliver strong load capacity, wear resistance, and durability. The left-hand thread design helps prevent loosening during operation, while the flange provides secure, even pressure distribution across the joint.
With a 1.25mm pitch, these bolts are well-suited for machinery housings, automotive components, and equipment where reverse-threaded fasteners are specified by design.
uxcell M10x20mm Left-Hand Flange Bolts
These M10 x 20mm flange bolts feature a 21mm flange diameter and a 14mm hex head width, with a 9mm head height. Made from 8.8-grade carbon steel and finished in black oxide, they provide high load capacity, hardness, and durability for demanding applications. The left-hand thread design helps mitigate loosening, and the flange portion acts as a flat washer to lock the bolt firmly in place during tightening.
They are appropriate for automotive or industrial projects where secure fastening and vibration resistance are critical.
Kozelo M8-1.25 x 50mm Left-Hand Bolts
Two-piece set featuring fully threaded M8-1.25 bolts with a 50mm length, carbon steel construction, and a black oxide finish. The DIN933-compliant hex head and left-hand external hex drive ensure a secure fit in mechanical and structural applications. With a 1.25mm pitch and robust threading, these bolts maximize engagement and resist loosening under operational stresses.
Suitable for interior construction, machinery assembly, and general-purpose repairs where reverse-threading is part of the design or required for preventing loosening in rotating assemblies.
Buying Guide: Key Purchase Considerations
- Thread direction and use case: Confirm left-hand threading is required to counteract vibration or rotation in your specific machine or assembly.
- Material and finish: 8.8-grade carbon steel with black oxide offers strong strength and wear resistance; stainless options excel in corrosion-prone environments.
- Dimensions and pitch: Match diameter, length, and thread pitch to the mating components and design tolerances for reliable engagement.
- Head style and flange design: Hex head vs. socket head, and flange vs. plain washer, affect installation space, torque, and load distribution.
- Coatings and durability: Black oxide provides a uniform finish and corrosion resistance, while stainless variants resist rust for outdoor use.
- Availability and packaging: Consider whether you need singles, pairs, or multi-pack sets to cover maintenance and replacements.
- Standards compliance: Look for DIN or ISO specifications to ensure compatibility with existing hardware and industry norms.
- Cost versus benefit: Higher-grade materials typically deliver longer service life, reducing replacement frequency in demanding environments.